I am troubleshooting some loss of fidelity when uploading InDesign-created epub to KDP, and I want to look at the epub as it is right after the Indesign export process, to check on HTML and CSS tags. I don't need to do any changes to the ePub.
I rename the file from
file.zip, and use macOS to unpack the zip by opening it with the archive utility. (This approach has worked fine for me for epubs I get from other sources.)
The Archive Utility reports: Unable to expand "file.zip". It is in an unsupported format.
I found a 2010 post on the web pointing to an AppleScript on another forum somewhere to do epub decompression. I have not tried this as I don't know it does anything other than rename and run the Archive Utility, as AppleScript is generally a lightweight tool.